Hey there, @Stefan59
Welcome to the Community!
There's a couple of things that could have happened here, depending on whether this was a totally brand new contract, or an additional line alongside an existing one.
If it's the latter, you're most likely seeing pro-rata charges - this is when you add a product to your account part-way through the month, so therefore are charged for that period on your next bill.
Our article here gives a good overview of these charges along with some other ways your bill can be higher, too.
Alternatively if you give our customer care team a call, they'll be able to bring up your details and say for sure what's happening here.
Peter
